logrus 学习笔记

logrus

实现多个实例

func New() *Logger {
	return &Logger{
		Out:          os.Stderr,
		Formatter:    new(TextFormatter),
		Hooks:        make(LevelHooks),
		Level:        InfoLevel,
		ExitFunc:     os.Exit,
		ReportCaller: false,
	}
}

默认实例

var (
	// std is the name of the standard logger in stdlib `log`
	std = New()
)

Pool 使用

// Reusable empty entry
entryPool sync.Pool
    
func (logger *Logger) newEntry() *Entry {
	entry, ok := logger.entryPool.Get().(*Entry)
	if ok {
		return entry
	}
	return NewEntry(logger)
}

func (logger *Logger) releaseEntry(entry *Entry) {
	entry.Data = map[string]interface{}{}
	logger.entryPool.Put(entry)
}

核心代码

entry log

// This function is not declared with a pointer value because otherwise
// race conditions will occur when using multiple goroutines
func (entry Entry) log(level Level, msg string) {
	var buffer *bytes.Buffer

	// Default to now, but allow users to override if they want.
	//
	// We don't have to worry about polluting future calls to Entry#log()
	// with this assignment because this function is declared with a
	// non-pointer receiver.
	if entry.Time.IsZero() {
		entry.Time = time.Now()
	}

	entry.Level = level
	entry.Message = msg
	entry.Logger.mu.Lock()
	if entry.Logger.ReportCaller {
		entry.Caller = getCaller()
	}
	entry.Logger.mu.Unlock()

	entry.fireHooks()

	buffer = getBuffer()
	defer func() {
		entry.Buffer = nil
		putBuffer(buffer)
	}()
	buffer.Reset()
	entry.Buffer = buffer

	entry.write()

	entry.Buffer = nil

	// To avoid Entry#log() returning a value that only would make sense for
	// panic() to use in Entry#Panic(), we avoid the allocation by checking
	// directly here.
	if level <= PanicLevel {
		panic(&entry)
	}
}

扩展实现

统一接口，面向接口开发

type Hook interface {
	Levels() []Level
	Fire(*Entry) error
}
type Formatter interface {
	Format(*Entry) ([]byte, error)
}
func (entry *Entry) fireHooks() {
	entry.Logger.mu.Lock()
	defer entry.Logger.mu.Unlock()
	err := entry.Logger.Hooks.Fire(entry.Level, entry)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to fire hook: %v\n", err)
	}
}

func (entry *Entry) write() {
	entry.Logger.mu.Lock()
	defer entry.Logger.mu.Unlock()
	serialized, err := entry.Logger.Formatter.Format(entry)
	if err != nil {
		fmt.Fprintf(os.Stderr, "Failed to obtain reader, %v\n", err)
		return
	}
	if _, err = entry.Logger.Out.Write(serialized); err != nil {
		fmt.Fprintf(os.Stderr, "Failed to write to log, %v\n", err)
	}
}